DESCRIPTION (applicant's abstract): The APS Conference on "Determinants of Vigilance: Interaction Between the Sleep and Circadian Systems" is scheduled for October 19-22, 1999 in Ft. Lauderdale, Florida. The Conference is designed to bring together scientists from all over the world who have been involved in research or have research interest in the circadian and the sleep fields. The fields of circadian biology and basic mechanisms of sleep have developed relatively independently. Yet it is clear that these two systems have major interactions and with respect to determining vigilance and performance they are inextricably coupled. The basis for this coupling is currently unknown. Not only do the two fields have little interaction but currently they use different experimental paradigms. The major paradigm that is used in the circadian rhythm field is a molecular/genetic approach based on mutants in species such as Drosophila and mice with abnormal circadian rhythm. The goal of these studies is to identify the molecular basis of the intrinsic biological clock and currently less attention is paid to how the clock affects the rest/activity or sleep/wake cycles. The sleep field, in contrast, has currently made little use of molecular/genetic approaches and the dominant paradigm that is used is a systems neuroscience one (electrophysiology, etc.). The meeting is designed to explore the nature of these two systems and how they might interact. The goals of the meeting are: (1) To assess the state of the art as to knowledge about the interaction between the sleep and circadian systems. (2) To provide a forum to stimulate interaction between the sleep and circadian scientific communities. (3) To facilitate the emergence of new research directions that can advance our understanding of the nature of the interaction. (4) To develop a publication that will serve as a current statement of where we are with respect to knowledge in this area and what scientific opportunities are perceived to exist.